The present invention relates to a process recovery of catalyst components from a reaction mixture and particularly to reaction mixture from oxidative direct carbonylation.
A process for the removal and recovery of quaternary salt (A) and base (D) from a reaction mixture is disclosed. The reaction mixture resulting from oxidative direct carbonylation contains in addition to (A) and (D), at least one hydroxyaromatic compound (B) and at least one reaction product (C) and optionally a solvent, and the process entails
a) adding acid to the reaction mixture to cause conversion of (D) into a hydroxyaromatic compound (B2) b) separating the reaction mixture into b1.) that contains (C) and optionally (B) and/or (B2) and b2.) that contains (A) and optionally (B) and/or (B2), and c) reacting b1.) with a base (E) to re-form (D).
During the oxidative direct carbonylation of aromatic hydroxy compounds in the presence of CO, O2 a noble metal catalyst, preferably palladium, and also an inorganic cocatalyst (e.g. manganese, or cobalt salts), a base, a quaternary salt, various organic cocatalysts (e.g., quinones or hydroquinones) and drying agents are generally used (see e.g. DE-OS 27 38 437, U.S. Pat. No. 4,349,485, U.S. Pat. No. 5,231,210, EP-A 677 336, EP-A 858 991, U.S. Pat. No. 5,760,272). The process may be performed in a solvent.
After performing the reaction, product mixtures are obtained from these reactions which contain, inter alia, one or more quaternary salts A, a hydroxyaromatic compound B, reaction products C such as e.g. water and diaryl carbonates, a base D (incl. any being produced by deprotonation of a hydroxyaromatic compound with another base or the directly used salt of a hydroxyaromatic compound) and possibly solvent, additional catalyst components, auxiliary substances and impurities. Thus, there is the object of separating one or more products C from quaternary salts and bases (A and D), without decomposing sensitive products C and also recycling A, B and D to the reaction as quantitatively as possible without any of the impurities present in the reaction mixture.
The working-up of such streams in the absence of D, by an extraction and precipitation process, is disclosed in EP A1 913 197. However, this working-up process does not lead directly to re-useable products without impurities.
An extraction process for recovering bromide salts from reaction mixtures similar to those in the present application is disclosed in U.S. Pat. No. B 6,310,232. Here again, however, the process does not lead directly to re-useable products A, B and D.